Stephen Amell reveals special guests for Arrow’s 100th episode Production is in full swing on Arrow‘s 100th episode and star Stephen Amell has taken to Twitter to continuously tease the episode and its special guests. Among those set to appear in the episode, which appears to be part of the epic four-show crossover, is a guest list that includes Grant Gustin as The Flash, Victor Garber as Martin Stein, Franz Drameh as Jefferson Jackson, Melissa Benoist as Supergirl, and the return of Deathstroke (whether that is another hallucination or the character’s true return remains to be seen).